GRAPE

Grapes are the edible berries produced by woody, deciduous vines in the genus Vitis of the Vitaceae family, with Vitis vinifera being the most widely cultivated species native to the Mediterranean basin, Central Europe, and southwestern Asia.^[1][2] These vines feature alternate leaves that vary in shape from unlobed to deeply lobed, measuring 2 to 10 inches long with toothed margins, and produce small, greenish-yellow, self-pollinating flowers in clusters that develop into bunches of round berries typically under 1 inch in diameter, enclosed in thin, waxy skins over juicy pulp containing 1 to 4 seeds.^[2] The fruits range in color from green and red to purple and black, depending on the variety, and are prized for their sweet-tart flavor.^[1] Domestication of grapes dates back to between 3500 and 1000 BCE, with evidence from ancient Egyptian hieroglyphics and widespread cultivation by Greek and Roman civilizations, where they were primarily used for winemaking, often diluted with water or herbs.^[2] European explorers and missionaries, including the Spanish in the 1700s, spread grape cultivation to the Americas and other regions, leading to the development of hybrid varieties adapted to diverse climates.^[2] As of 2024, grapes are grown on approximately 71,000 square kilometers of vineyards worldwide, with major producers including Spain (9,300 km²), France (7,830 km²), and Italy (7,280 km²); the global area has been declining by about 0.6% annually in recent years due to climate and market factors.^[3] Grapes thrive in full sun and well-drained soils such as loam, clay, or sand with a pH of 6.0 to 8.0, requiring support structures like trellises and regular pruning to control growth and maximize fruit yield; they are hardy in USDA zones 6a to 10b but demand protection from frost, winter winds, and pests like phylloxera.^[1] Global grape production in 2024 is estimated at 77.7 million metric tons, with approximately 53% destined for wine, 45% for fresh table grapes, and 2% for drying into raisins, while seeds yield oil and the vines serve ornamental purposes in landscapes.^[4][3] Nutritionally, raw grapes provide about 69 calories per 100 grams, consisting mostly of water (81 g), with notable potassium (191 mg), fiber (0.9 g), and antioxidants like resveratrol, which may support heart health and reduce inflammation.^[2] Economically, the grape and wine industry is vital, contributing over $323 billion annually to the U.S. economy as of 2025, where the average person consumes about 8.5 pounds of fresh grapes yearly, underscoring its role in agriculture, viticulture, and global trade.^[5][6]

Biology

Botanical Characteristics

Grapes are woody, deciduous vines belonging to the genus Vitis within the family Vitaceae, with Vitis vinifera serving as the principal species for domestication and cultivation worldwide.^[1][2] These perennial climbers can extend 12 to 30 meters in length, utilizing forked tendrils that emerge opposite the leaves to grasp supports and facilitate upward growth.^[2][7] The stems display a characteristic zigzag pattern, featuring flaky bark on mature wood and smoother bark on younger sections.^[2][8] Leaves are alternately arranged, simple, and palmate with 3 to 7 lobes, often serrated or dentate along the margins, and measure 5 to 20 cm in length and width, with a slightly fuzzy underside in some varieties.^[1][7] These compound-like leaves contribute to the vine's photosynthetic capacity, supporting vigorous growth in temperate climates. Flowers are small, greenish-yellow, and inconspicuous, borne in pendulous panicles or clusters that develop from buds opposite the tendrils.^[1][2] Most cultivated V. vinifera varieties produce hermaphroditic (perfect) flowers, featuring both functional stamens and pistils, though wild Vitis species often exhibit dioecious forms with separate male and female plants.^[9][2] Grapevine flowers are primarily self-pollinating due to their hermaphroditic nature, with pollen transferring within the same flower or vine. The calyptra—a fused corolla—abscises during bloom in late spring to expose the reproductive organs.^[10][9][2] Fruit develops as berries in compact bunches, each berry oval to round and typically 1 to 3 cm in diameter, protected by a thin, waxy exocarp (skin), enclosing juicy mesocarp (flesh) and 1 to 4 endocarpic seeds.^[7][2] Berry colors range from green to red, purple, or black, with a glaucous bloom on the surface; seedless cultivars arise from stenospermocarpy, where seeds abort early in development.^[1][2] The grapevine's life cycle is adapted to temperate zones, commencing with winter dormancy when the plant sheds leaves and conserves energy in woody tissues.^[7] Bud break occurs in early spring, initiating new shoot growth and leaf expansion, followed by flowering in mid-to-late spring.^[9] Veraison marks the critical summer phase of berry softening, color change, and sugar accumulation, culminating in harvest during fall when fruits reach physiological maturity.^[7] Wild relatives, such as Vitis riparia, impart valuable traits like enhanced cold hardiness, enabling survival at temperatures down to -40°C in fully acclimated tissues.^[11][12]

Varieties and Classification

Grapes belong primarily to the genus Vitis, with Vitis vinifera L. representing the dominant species, accounting for the majority of global grape production due to its widespread cultivation for wine, table, and dried fruit uses.^[13] This Eurasian species encompasses more than 10,000 cultivars, many of which are synonyms or regional clones, contributing to its vast genetic diversity.^[14] Other significant classifications include American species such as Vitis labrusca L., known for varieties like Concord, which are prized for their cold hardiness and use in juice and jelly production, and interspecific hybrids that combine traits from V. vinifera and native North American species to enhance adaptability.^[15] These hybrids, including French-American types developed in the 19th and 20th centuries, address limitations like phylloxera susceptibility in V. vinifera.^[16] Varieties within these groups are further categorized by primary purpose: table grapes for fresh consumption, such as the seedless Thompson Seedless; wine grapes like Cabernet Sauvignon and Chardonnay, valued for their distinct flavors and aromas; and raisin grapes, exemplified by Sultana (a synonym for Thompson Seedless when dried).^[17] Ampelography, the science of identifying grapevines through morphological traits like leaf shape, cluster density, and berry characteristics, plays a crucial role in distinguishing these cultivars, especially in germplasm collections.^[17] Seedless varieties, predominantly in V. vinifera, arise through stenospermocarpy, a process where fertilization occurs but seed development arrests early, resulting in rudimentary seed traces and larger, edible berries.^[18] This trait, genetically linked to a locus on chromosome 18, has been bred into cultivars like Flame Seedless to meet consumer preferences for convenience.^[18] Recent breeding efforts have focused on hybrids for disease resistance, particularly the PIWI (Pilzwiderstandsfähig) varieties developed in Germany since the late 20th century, incorporating genes from resistant species like Vitis amurensis to combat fungal pathogens such as downy and powdery mildew without fungicides.^[19] Examples include Regent and Johanniter, which blend V. vinifera quality with enhanced resilience, promoting sustainable viticulture.^[19]

History

Origins and Domestication

The genus Vitis, which includes grapes, originated in North America, with fossil evidence of Vitaceae family seeds dating back to the Eocene epoch approximately 55-34 million years ago in western North American deposits.^[20] Over time, the genus diversified, leading to native species in both North America and Eurasia; the wild progenitor of the domesticated grape, Vitis vinifera subsp. sylvestris, is primarily found in the Caucasus region, western Asia, and parts of Europe.^[21] This wild form, characterized by dioecious flowering (separate male and female plants) and small, acidic berries, represents the evolutionary baseline from which human selection began.^[22] Archaeological and genetic evidence indicates that grape domestication occurred in the South Caucasus, particularly in modern-day Georgia, around 6000-5800 BCE during the early Neolithic period.^[23] Biomolecular analysis of pottery residues from sites like Shulaveris Gora has revealed tartaric acid, a biomarker for grape wine, confirming early viniculture practices.^[23] By 3000 BCE, cultivation had spread to Mesopotamia and Egypt, where grape seeds and wine residues appear in Predynastic Egyptian sites and Sumerian records, marking the integration of grapes into early urban societies.^[24] In Sumer, wine production became a key cultural element, with cuneiform texts from around 2100 BCE describing viticulture and fermentation, though earlier archaeological finds suggest routine use by the third millennium BCE.^[24] Domestication drove significant genetic shifts in V. vinifera, including the selection for hermaphroditic flowers to enable self-pollination and higher yields, as well as larger berry size, increased sugar content, and seedless or less bitter varieties for palatability.^[21][22] These changes, evidenced by morphometric analysis of ancient seeds showing larger pips compared to wild forms, reflect human preference for traits suited to wine and food production.^[21] A major setback occurred in the late 19th century with the phylloxera epidemic, an aphid (Daktulosphaira vitifoliae) introduced to Europe from North America, which devastated V. vinifera vineyards between 1863 and 1890.^[25] The crisis was mitigated by grafting European scions onto resistant American rootstocks, such as Vitis riparia and Vitis rupestris, preserving domesticated lineages.^[26] Modern grape varieties are largely derived from this ancient domesticated stock, with ongoing genetic diversity traced back to Neolithic selections.^[22]

Global Spread and Historical Cultivation

The dissemination of grape cultivation beyond its Near Eastern origins began in antiquity, with the Phoenicians playing a pivotal role in introducing viticulture to the western Mediterranean around 800 BCE, including regions like Iberia and North Africa through trade and colonization.^[27] The Romans further expanded this practice across the Mediterranean basin and into Europe, building on viticulture introduced to Italy by the Etruscans and Greeks around the 2nd–1st millennium BCE, and extending cultivation northward to Gaul (modern France) by the first centuries CE, where it adapted to cooler climates along river valleys.^[28][29] A 2025 study of ancient grape seeds indicates that domestication in Italy was a gradual process beginning in the Late Bronze Age, spanning thousands of years with ongoing selection for local varieties.^[30] By the 16th century, Spanish explorers introduced European Vitis vinifera varieties to the Americas, with initial plantings in Mexico during the 1520s and subsequent spread to South America, marking the beginning of New World viticulture despite early challenges from local pests and climates.^[31] During the medieval period, European monastic orders, particularly the Benedictines and Cistercians, preserved and refined grape cultivation techniques amid societal disruptions, maintaining vineyards in regions like Burgundy and Champagne for sacramental wine production and economic sustenance.^[32] Colonial expansion in the 18th and 19th centuries propelled further global dissemination; European varieties arrived in Australia with the First Fleet in 1788, planted by Governor Arthur Phillip in New South Wales to support settlement.^[33] In the Americas, Franciscan missionaries introduced Mission grapes—a resilient Vitis vinifera variety—to California in 1769 at the San Diego Mission, establishing foundational vineyards that spread along the coastal missions.^[34] The 19th century brought severe setbacks with the phylloxera epidemic, an aphid pest inadvertently imported from North America, which devastated about 40% of French vineyards, contributing to widespread losses across Europe between 1863 and 1890, prompting recovery through grafting European scions onto phylloxera-resistant American rootstocks.^[35] In response, French breeders developed interspecific hybrids, crossing European vines with American species to enhance pest resistance while retaining quality traits.^[36] The 20th century witnessed varied impacts from geopolitical events and economic forces. In the United States, Prohibition from 1920 to 1933 initially spurred a surge in vineyard plantings—nearly doubling in California—as growers shifted to table grapes and juice concentrates for home winemaking, though it ultimately led to widespread uprooting after repeal.^[37] Post-World War II economic recovery fueled a boom in table grape production, particularly in California, where irrigation advancements and market demand expanded cultivation from traditional wine varieties to seedless types like Thompson Seedless, supporting fresh fruit exports.^[38] Globalization in the late 20th century accelerated shifts, transforming wine from a low-trade commodity to one of the most globally exchanged agricultural products, with increased cultivation in emerging regions like Australia and the Southern Hemisphere driven by technological transfers and rising international demand.^[39]

Cultivation

Environmental Requirements

Grapevines thrive in Mediterranean climates characterized by warm, dry summers and cool, wet winters, which provide optimal conditions for growth and fruit development.^[40] These regions typically feature warm days with temperatures averaging 25–30°C to promote photosynthesis and ripening, coupled with cool nights below 20°C that preserve acidity in the berries.^[41] Annual rainfall of 700–1000 mm, concentrated in the winter months, supports vine establishment without excess during the growing season, as overly wet conditions can foster diseases.^[42] Temperature thresholds are critical: bud break generally requires sustained averages above 10°C, while flowering and fruit set demand frost-free periods to avoid damage from temperatures below 0°C.^[43][44] Soil preferences for grape cultivation emphasize well-drained loamy or gravelly types that prevent waterlogging and allow deep root penetration for nutrient uptake.^[45] An optimal pH range of 6–7 facilitates mineral availability, with acidic soils below 6 risking aluminum toxicity and alkaline ones above 8 limiting iron and zinc absorption.^[45] The terroir concept highlights how soil minerals, such as those in limestone or schist, influence grape flavor by affecting nutrient assimilation and metabolite production, contributing to distinctive varietal aromas like methoxypyrazines in certain cultivars.^[41] Site selection plays a pivotal role in meeting environmental needs, with gentle slopes of 2–15% promoting natural drainage and reducing frost risk through cold air flow.^[46] Elevations up to 500–600 m enhance diurnal temperature variations, aiding balanced ripening by cooling nights while maximizing daytime heat.^[47] In arid regions, supplemental irrigation is essential to mitigate water stress, typically delivering 300–500 mm annually via drip systems to maintain vine vigor without excess moisture.^[48] Grapevines require heat summation measured in growing degree days (GDD), calculated from a base of 10°C, with many varieties needing 1500–2500 GDD from bud break to harvest for full ripening.^[49] Varieties like cold-hardy hybrids may mature with as few as 2000 GDD (base 10°C), while warmer-climate cultivars demand more to achieve optimal sugar and phenolic development.^[50] Grapes remain vulnerable to environmental extremes, including drought that impairs photosynthesis and yield, and hail that causes direct berry damage, potentially reducing harvests by 20–50% in affected areas.^[51][52] Emerging practices, such as drought-resistant rootstocks and advanced irrigation, are increasingly adopted to address climate change impacts like shifting growing zones as of 2025.^[53]

Viticultural Techniques

Viticultural techniques encompass a range of practices aimed at establishing and maintaining productive grapevines while optimizing fruit quality and vine health. Vineyard establishment begins with rootstock selection, particularly to combat phylloxera, a root-feeding insect that devastated European vineyards in the 19th century; phylloxera-resistant rootstocks, often derived from North American Vitis species like V. riparia or V. rupestris, are grafted to desired scion varieties to provide resistance while adapting to local soil, climate, and vigor needs.^[54][55] Planting density typically involves spacing vines 1.5 to 2.4 meters apart within rows and 2.4 to 3.7 meters between rows, achieving 1,100 to 2,800 vines per hectare, which balances yield potential with resource competition and facilitates mechanization.^[56][57] Trellis systems, such as the Guyot method, support vine growth by training a single cane with 6 to 10 buds along a wire, followed by renewal spurs, promoting balanced fruiting and ease of management in cooler climates.^[58][59] Ongoing management practices focus on yield control and vine vigor through pruning, conducted during dormancy from late winter to early spring, where growers remove excess wood to leave 20 to 40 buds per vine based on previous season's growth, ensuring a balance between vegetative development and fruit production.^[60][61] Canopy management enhances light exposure and air circulation by techniques like shoot thinning, leaf removal near clusters, and hedging, which increase sunlight penetration to fruit zones by up to 50%, improving berry composition and reducing disease incidence.^[62][63] Pest control employs integrated pest management (IPM) strategies, prioritizing cultural methods such as open canopies to deter powdery and downy mildew—fungal diseases caused by Erysiphe necator and Plasmopara viticola—followed by targeted applications of sulfur-based fungicides or biological agents like mycophagous mites when thresholds are exceeded.^[64][65] Harvesting timing is determined by monitoring sugar-acid balance, with wine grapes typically picked at 22 to 24° Brix (measured via refractometer) to achieve optimal ripeness, often verified through berry sampling of 100 fruits across multiple vines.^[66][67] Hand-picking remains prevalent for premium varieties to minimize cluster damage and select quality, while mechanical harvesters, using vibrating rods to shake berries from vines, enable efficient large-scale operations in uniform vineyards, though they require precise timing to avoid unripe or overripe inclusions.^[68][69] Sustainable practices, including organic farming, avoid synthetic pesticides and fertilizers, relying instead on cover crops, compost, and biodiversity enhancement to maintain soil health and reduce erosion, as promoted in programs like VineBalance for northeastern U.S. viticulture.^[70][71] Recent innovations in precision agriculture, adopted widely since the 2010s, utilize drones equipped with multispectral cameras to map vineyard variability, detect early disease signatures like mildew through image analysis, and guide targeted interventions, improving resource efficiency by 20-30% in monitored fields.^[72][73]

Production and Economics

Major Producing Regions

Europe stands as the dominant continent for wine grape production, with France, Italy, and Spain collectively accounting for over half of the world's wine output in 2024, as the European Union produced approximately 138.3 million hectoliters, representing about 61% of global totals.^[3] Preliminary estimates from the OIV indicate global wine production for 2025 at 228 to 235 million hectoliters, with a mid-range of 232 million hectoliters, reflecting a 3% increase from 2024.^[74] In France, the Bordeaux region is particularly renowned for its red wines, specializing in blends dominated by Cabernet Sauvignon and Merlot grapes that thrive in the area's gravelly soils and maritime climate.^[75] Italy's diverse terroirs, from Tuscany to Piedmont, support a wide array of premium wines, while Spain's Rioja and Ribera del Duero areas emphasize robust reds from Tempranillo. These regions face ongoing challenges from climate change, including shifting growing zones northward and increased risks of heatwaves that accelerate ripening and alter grape composition.^[76] In the Americas, California in the United States emerges as a powerhouse, with Napa Valley celebrated for its premium Cabernet Sauvignon-based wines that command high prices due to the region's cool fog-influenced microclimates and hillside vineyards.^[77] Argentina's Mendoza province, nestled in the Andes foothills, excels in high-altitude Malbec production, benefiting from intense sunlight and dry conditions ideal for concentrated flavors. Chile serves as a key hub for table grapes, with its Central Valley providing year-round exports thanks to the Southern Hemisphere's counter-seasonal harvest and efficient irrigation systems.^[78] Water scarcity poses a significant challenge here, exacerbated by prolonged droughts that strain Andean river sources.^[76] Asia has seen rapid expansion in grape cultivation, led by China, which has become the world's largest producer overall, primarily focusing on table grapes in regions like Xinjiang and Hebei where vast arid plains support large-scale farming with drip irrigation.^[4] India is an emerging player, particularly in Maharashtra's Nashik district, known as the grape capital, where table grape varieties flourish in the tropical-subtropical climate, driving exports to Europe and the Middle East.^[79] Other notable regions include Australia and South Africa. Australia's Barossa Valley and Hunter Valley produce bold Shiraz and Chardonnay, with recent adaptations to drought involving the development of mildew- and drought-resistant grapevines to sustain yields amid erratic rainfall.^[80] In South Africa, the Western Cape's Stellenbosch and Paarl areas dominate, leveraging Mediterranean-like conditions for Pinotage and Chenin Blanc, though producers grapple with water restrictions in this semi-arid zone.^[81] Across these regions, climate change is prompting innovations like precision irrigation and varietal shifts to maintain viability as temperatures rise and precipitation patterns become unpredictable.^[76]

Global Output and Trade

Global grape production reached an estimated 77.7 million tonnes in 2024, marking a 3.7% increase from 2023's approximately 74.9 million tonnes, with output stabilizing around this level since 2013.^[4] The global vineyard area continued to decline, contracting by 0.6% to 7.1 million hectares in 2024.^[3] China leads as the top producer with 17.0 million tonnes in 2024, accounting for 22% of the global total, followed by Italy at 7.3 million tonnes (9%) and the United States at 6.4 million tonnes (8%).^[4] Yields vary regionally, with a global average of 10.9 tonnes per hectare in 2024; higher yields of 15-20 tonnes per hectare occur in table grape-focused areas like parts of China and India, while wine grape regions in Europe often range from 8-12 tonnes per hectare due to denser planting and quality emphasis.^[4][82] International trade in fresh grapes expanded to 5.0 million tonnes in volume and €9.9 billion in value in 2024, reflecting a 4.2% volume increase from 2023 amid rising demand for table varieties.^[4] Major exporters include Chile, Peru, Italy, and South Africa, which together dominate shipments to key markets, while leading importers are the United States (importing $2.72 billion worth in 2023), the European Union ($1.27 billion), and Germany ($0.97 billion).^[83][84] Fresh grapes constitute the bulk of trade volume at around 70-80%, with processed products like raisins and wine musts comprising the remainder, though fresh exports have grown faster due to global preferences for ready-to-eat produce.^[4][85] Table grape production, which accounts for about 43% of global fresh grape output, has shown robust growth, reaching 33.3 million tonnes in 2024—a doubling from 2000 levels driven by an annual increase of 3.1% and expanding consumer demand in Asia and North America.^[4] The 2020s have seen trade disruptions from supply chain issues, including a 35% rise in logistics costs since 2020, which elevated export prices and temporarily constrained volumes during peak seasons.^[86] Post-2022 developments include stricter EU pesticide regulations under Regulation (EC) No 396/2005, enforcing maximum residue levels that have led to export restrictions for non-compliant shipments from major producers like Turkey and India, while sustainable certifications such as GlobalG.A.P. have become essential for accessing premium markets.^[87][88] Grape cultivation plays a vital economic role in rural development, serving as a high-value crop that supports local employment and income diversification; for instance, in regions like California's Central Valley and China's Xinjiang, it generates billions in revenue and sustains smallholder farming communities through direct sales to wineries and exporters.^[89][90]

Culinary and Industrial Uses

Fresh Consumption and Table Grapes

Table grapes are prized for their suitability as a fresh snack due to their crisp texture, high sugar content typically ranging from 15 to 20° Brix, and vibrant colors including green, red, and black.^[91][92][93] Seedless varieties dominate the global market, accounting for the majority of production because of consumer preference for convenience and ease of eating without pits.^[94] Global per capita consumption of fresh table grapes averages around 3-5 kg per year, with higher rates in regions like Europe at approximately 3.25 kg annually.^[95][96] Seasonal availability is extended through advanced storage techniques, such as controlled atmosphere systems that maintain quality for up to three months by regulating oxygen, carbon dioxide, and temperature levels.^[97] Breeding programs have focused on enhancing shelf-life and flavor profiles to meet market demands, exemplified by the Cotton Candy grape developed in the 2010s through crossbreeding for its candy-like taste and firmness.^[98] Recent hybrid varieties like Autumn Crisp, a seedless green type released by Cornell University, offer improved storability and crispness for late-season harvests.^[99] Their nutritional appeal as low-calorie snacks rich in antioxidants and vitamins further boosts popularity, often positioning them as healthy alternatives in daily diets.^[100] In culinary contexts, fresh table grapes play versatile roles, commonly featured in salads for their juicy burst and sweetness or in desserts like creamy grape salads mixed with cream cheese and nuts.^[101][102]

Processed Products

Grapes are transformed into raisins through dehydration processes that remove approximately 80% of their water content, concentrating their flavors and nutrients. Traditional sun drying involves spreading harvested grapes on trays or paper in open fields, where they are exposed to sunlight for 2 to 4 weeks until the moisture level drops to 14-18%, a method still predominant in regions like California's San Joaquin Valley.^[103] Artificial drying, using mechanical dehydrators or hot air ovens at controlled temperatures of 60-70°C, accelerates the process to 24-48 hours and is employed to mitigate weather risks or achieve uniform quality, particularly for premium varieties.^[104] Common raisin types include sultanas, produced from the Thompson Seedless grape variety, which are light-colored and seedless; and currants, derived from the smaller Zante currant (Black Corinth) grapes, known for their intense sweetness and use in baking.^[105] Global raisin production reached approximately 1.3 million metric tons in recent years, with major contributors including Turkey, the United States, and Iran.^[106] Modern dehydration technologies, such as indirect solar dryers, have gained traction in California during the 2020s to enhance efficiency and product safety. These systems use enclosed chambers to capture solar heat while protecting grapes from contaminants like dust and insects, reducing drying time by up to 50% compared to open sun methods and minimizing fungal growth, such as ochratoxin A-producing molds.^[107] The drying process also intensifies nutritional profiles; for instance, raisins contain about 3.7 grams of dietary fiber per 100 grams—roughly four times the amount in fresh grapes (0.9 grams per 100 grams)—due to the removal of water, promoting better digestive health when consumed in moderation.^[108] Grape juice is extracted by crushing and pressing the fruit to separate the liquid from the solids, often using enzymatic treatments to improve yield and clarity. The juice undergoes flash pasteurization, typically heating to 85-88°C for at least one minute, to eliminate pathogens while preserving sensory qualities like color and aroma.^[109] For concentrates used in beverages and food products, the juice is evaporated under vacuum to remove water, achieving up to 68° Brix concentration without significant nutrient loss. Byproducts from extraction include pomace, the residual skins, seeds, and pulp, which comprises 20-25% of the grape's weight and is repurposed for animal feed or further extraction of compounds like polyphenols.^[110] Vinegars are produced by fermenting grape must—the freshly pressed juice including skins and seeds—first into alcohol via yeast, then into acetic acid through bacterial oxidation. Traditional balsamic vinegar, originating from regions like Modena and Reggio Emilia in Italy, starts with cooking the must to caramelize sugars, followed by aging in wooden barrels for 12 to over 25 years, resulting in a dense, syrupy product with complex flavors.^[111] Other grape vinegars use uncooked must for milder profiles. Jams and jellies are made by simmering grape pulp or juice with sugar and pectin to reach a gel-like consistency, often at 105°C, allowing preservation through high sugar content that inhibits microbial growth.^[112]

Wine and Beverage Production

The production of wine from grapes primarily involves the transformation of grape sugars into alcohol through fermentation, a process that has been refined over centuries. After harvesting, grapes are crushed to release their juice, known as must, which includes skins, seeds, and sometimes stems. This step is followed by maceration for certain wines, where the must soaks to extract flavors and compounds. Fermentation then occurs as yeast converts the natural sugars in the must to ethanol and carbon dioxide, typically resulting in wines with an alcohol by volume (ABV) of 12-15%.^[113][114] Following primary fermentation, the wine undergoes clarification to remove solids and is aged in barrels, tanks, or bottles to develop complexity, with oak barrels often imparting tannins and vanilla notes.^[114] The type of wine produced depends on the handling of grape skins, which contain pigments, tannins, and flavors. Red wines are made from dark-skinned grapes where the skins remain in contact with the fermenting must for days to weeks, extracting color, tannins for structure, and phenolic compounds. In contrast, white wines, which can come from either light- or dark-skinned grapes, are pressed early to separate the juice from the skins before fermentation, yielding lighter colors and flavors focused on fruit acidity. Rosé wines achieve their pink hue through brief skin contact—often just hours to a day—with dark grapes, balancing elements of both red and white styles.^[115][116] Sparkling wines, such as those produced via the traditional Champagne method, start with a base still wine that undergoes a secondary fermentation to generate carbonation. In this process, a mixture of sugar and yeast (liqueur de tirage) is added to the bottled base wine, where the yeast ferments the sugar, producing carbon dioxide that dissolves under pressure to create bubbles; this secondary fermentation typically adds about 1.3% more alcohol.^[117][118] Beyond standard table wines, grapes contribute to fortified wines and distilled spirits. Fortified wines like Port are produced by halting fermentation midway through the addition of grape brandy, preserving residual sugars and boosting alcohol content to around 20% ABV; Port is typically made from red grapes in Portugal's Douro Valley. Grape brandy, such as grappa, is distilled from the pomace—the leftover skins, seeds, and stems after pressing—resulting in a clear, high-proof spirit often enjoyed as a digestif.^[119][120] Global wine production reached approximately 226 million hectoliters in 2024, the lowest level in over 60 years, influenced by climatic challenges across major regions. Varietal labeling, such as "Pinot Noir," requires that at least 75% of the grapes used be of the named variety under U.S. regulations, allowing consumers to identify wines by dominant grape characteristics like the light-bodied, cherry notes of Pinot Noir. Since 2020, trends toward low-alcohol wines (under 12% ABV) have grown, driven by health-conscious consumers seeking lighter options without sacrificing flavor, with production techniques like early harvesting or dealcoholization gaining prominence.^{[3][121][122]}

Nutritional Profile

Macronutrients and Basic Composition

Grapes are predominantly water-rich fruits, comprising about 80% water by weight, which contributes to their juicy texture and low caloric density. In a typical 100-gram serving of raw, seedless grapes (red or green European varieties), the energy content is approximately 69 kcal, derived primarily from carbohydrates that make up 18.1 grams, of which sugars—mainly glucose and fructose—account for 15.5 grams. This carbohydrate profile provides a quick but moderate energy source, with the glycemic index of grapes ranging from 43 to 59, placing them in the low to moderate category for blood sugar impact.^[123][124] Proteins and fats are minimal in grapes, offering just 0.72 grams of protein and 0.16 grams of total fat per 100 grams, making them a low-fat, low-protein food suitable for various dietary needs. Dietary fiber totals 0.9 grams per 100 grams, primarily located in the skin, which supports digestive health when consumed whole. These values are based on standard USDA analyses and show little variation across common varieties, though processing and cultivar can influence specifics.^[123] Variations exist between table grapes and wine grapes in macronutrient emphasis; table grapes typically exhibit 15-20% sugar content for fresh eating appeal, while wine grapes are harvested at higher levels (24-26% Brix, equivalent to sugar percentage) to support fermentation, resulting in denser carbohydrate profiles. Dried forms like raisins concentrate these nutrients through dehydration, yielding about 299 kcal per 100 grams, with 79.2 grams of carbohydrates (59 grams sugars) and 3.7 grams of fiber, alongside elevated protein at 3.1 grams. Studies, including recent USDA evaluations, indicate no substantial macronutrient differences between organic and conventional grapes, with compositions remaining comparable across production methods.^[125][126]

Vitamins, Minerals, and Bioactive Compounds

Grapes provide several essential vitamins, with vitamin C (ascorbic acid) present at approximately 3.2 mg per 100 g, primarily concentrated in the skin where it contributes to antioxidant activity.^[127] Vitamin K (phylloquinone) is found at 14.6 µg per 100 g (12% of the US Adequate Intake for adult males), supporting blood clotting and bone health, while vitamin B6 (pyridoxine) occurs at 0.086 mg per 100 g, aiding in metabolism and neurotransmitter synthesis.^[127] Grapes contain no vitamin B12 or vitamin D, contributing 0% to the US RDA for adult males per 100 g serving. Choline is present in low amounts, providing less than 5% of the US Adequate Intake for adult males. All other vitamins contribute less than 5% of the US RDA for adult males per 100 g. These values are based on USDA data and align with analyses of Indian grape varieties from IFCT 2017.^[127][128] These vitamins complement the macronutrient base by enhancing the fruit's role in delivering micronutrients alongside carbohydrates and fiber. Among minerals, grapes are a notable source of potassium at 191 mg per 100 g (6% of the US Adequate Intake for adult males), which helps regulate fluid balance and nerve signals.^[127] Copper is present at 0.127 mg per 100 g, involved in iron absorption and connective tissue formation, and manganese at 0.071 mg per 100 g, functioning as a cofactor in enzyme reactions.^[127] Trace elements like selenium appear in small amounts, around 0.1 µg per 100 g (0% of the US RDA for adult males), contributing to antioxidant defense systems.^[127] All other minerals contribute less than 5% of the US RDA for adult males per 100 g. These values are based on USDA data and align with analyses of Indian grape varieties from IFCT 2017.^[127][128] Grapes are rich in bioactive compounds, particularly polyphenols such as flavonoids, which are abundant in the skin and seeds and exhibit antioxidant properties.^[129] Resveratrol, a stilbene polyphenol, is found in red grape varieties at levels ranging from 0.2 to 5 mg per kg of whole fruit, with higher concentrations in the skins.^[130] Anthocyanins, responsible for the pigmentation in red grapes, are present at about 20–80 mg per 100 g in the skin of colored varieties, varying by cultivar and growing conditions.^[131] Grape pomace, the byproduct of winemaking, serves as a valuable source for extracting these polyphenols, including proanthocyanidins and phenolic acids.^[132] Ellagic acid, a phenolic compound derived from ellagitannins, occurs in grapes, particularly in muscadine varieties, though in lower amounts compared to berries like raspberries.^[133] Recent studies from 2020 to 2024 have explored ellagic acid's interactions with gut microbiota, highlighting its potential to modulate microbial composition through metabolism into urolithins, as reviewed in comprehensive analyses of polyphenol-microbiome dynamics.^[134]

Health Implications

Potential Benefits

Grapes and their derivatives, rich in polyphenols such as resveratrol, have been associated with cardiovascular health benefits primarily through antioxidant mechanisms that mitigate oxidative stress. Resveratrol, a key stilbenoid found in grape skins, attenuates oxidized low-density lipoprotein (oxLDL)-induced signaling and apoptosis in endothelial cells, thereby reducing the risk of atherosclerosis.^[135] A 2015 meta-analysis of randomized controlled trials demonstrated that daily intake of grape polyphenols significantly lowers systolic blood pressure by approximately 1.48 mmHg compared to controls, supporting their role in hypertension management.^[136] Polyphenols in grapes exhibit anticancer properties by inhibiting tumor growth and proliferation in various models. Extracts from muscadine grapes, high in polyphenols, suppress triple-negative breast cancer cell proliferation through modulation of signaling pathways.^[137] Similarly, grape-derived polyphenols reduce colon tumor growth by 31% in animal models, accompanied by decreased vascularization and metastasis.^[138] These compounds also confer anti-inflammatory effects; for instance, grape seed extract supplementation inhibits lipid peroxidation and modulates inflammatory markers, contributing to reduced systemic inflammation.^[139] Clinical evidence further indicates that topical application of grape seed extract 2% cream accelerates wound healing by promoting endothelial growth factor release and skin contraction.^[140] Beyond cardiovascular and anticancer effects, grapes offer benefits for eye health, diabetes management, and cognitive function. Regular consumption of grapes enhances macular pigment optical density, a marker of retinal protection against age-related macular degeneration, likely due to their carotenoid content including lutein and zeaxanthin.^[141] With a low glycemic index and load, grapes elicit minimal postprandial glucose spikes, making them suitable for type 2 diabetes management without compromising glycemic control.^[142] Flavonoids in Concord grape juice improve memory function and cognitive performance in older adults with mild impairment, enhancing episodic memory and attention after chronic supplementation.^[143] Incorporation of grapes aligns with the Mediterranean diet, which emphasizes fruit intake and correlates with reduced cardiovascular disease incidence through polyphenol-mediated protection.^[144] Recent research highlights grape pomace supplements—byproducts rich in polyphenols—as modulators of the gut microbiome; a 2023 review notes their ability to increase microbial diversity and alleviate obesity-related dysbiosis in preclinical models, suggesting potential probiotic-like benefits for human metabolic health.^[145] As of 2025, emerging studies indicate that long-term grape consumption supports kidney health by protecting against fibrosis in animal models and that fresh grapes contain over 1,600 bioactive compounds promoting heart, brain, skin, and gut health.^[146][147]

Risks and Toxicity

Grapes cultivated conventionally often harbor pesticide residues on their skins, which can include multiple chemicals linked to health risks such as endocrine disruption, developmental delays, and increased cancer potential upon chronic exposure.^[148][149] Washing or opting for organic varieties mitigates but does not eliminate these concerns, as residues may penetrate the fruit.^[150] The high natural sugar content in grapes, primarily fructose, poses risks for individuals with diabetes or insulin resistance, potentially causing rapid blood glucose spikes if consumed in large quantities despite their moderate glycemic index of around 45-59.^[151][142] Sulfite sensitivities, though rare, affect approximately 1% of the population and can trigger asthma-like symptoms, hives, or gastrointestinal distress in response to preservatives added during processing of grapes into wine, juice, or dried products.^[152][153] Grapes and raisins pose a severe toxicity risk to dogs, inducing acute kidney injury or failure in susceptible individuals, although not all dogs are affected and toxicity occurs idiosyncratically; a concern highlighted by the ASPCA since the early 2000s following initial case reports.^[154] The precise mechanism is not fully elucidated, but tartaric acid, a naturally occurring compound concentrated in these fruits, is implicated as the primary nephrotoxin, leading to renal tubular damage.^[154][155] Toxicity thresholds vary by individual sensitivity, but clinical signs have occurred at doses as low as 2.8 g/kg body weight for raisins and 19.6 g/kg for fresh grapes, with even smaller amounts potentially harmful in susceptible dogs.^[156] Initial gastrointestinal symptoms—vomiting, diarrhea, and anorexia—typically emerge within 6-12 hours of ingestion, progressing to lethargy, abdominal pain, oliguria, and elevated blood urea nitrogen/creatinine levels indicative of kidney failure by 24-72 hours.^[155][157] Prompt veterinary intervention is critical, involving emetic administration if within 2 hours of exposure, intravenous fluid diuresis to flush the kidneys, antiemetics, and serial monitoring of renal function; survival rates exceed 90% with early treatment but drop sharply if anuria develops.^[157][158] A 2024 scoping review of over 1,100 cases confirmed no statistically significant varietal differences in toxicity outcomes between red and white grapes or fresh versus dried forms, though tartaric acid concentrations may fluctuate based on cultivar, ripeness, and processing.^[159] Vineyard management frequently relies on copper-based fungicides and other agrochemicals, resulting in runoff that elevates heavy metal and pesticide levels in adjacent waterways, threatening aquatic life through bioaccumulation and ecosystem disruption.^[160][161] Excessive grape intake in humans can provoke digestive disturbances, including bloating, cramping, diarrhea, and gastric irritation, attributable to their sorbitol and fiber load overwhelming gut tolerance.^[162]